cisco workshop

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# Tagging cisco: Lessons from the Les Cheneaux Islands

## Todd Hayden, Chris Holbrook

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# Acknowledgments

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- Hammond Bay Biological Station
- Michigan Department of Natural Resources
- US Fish and Wildlife Service
- Real-Time Aquatic Ecosystem Observation Network
- Great Lakes Fishery Commission
- Great Lakes Acoustic Telemetry Observation System
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# History

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- 2017 field tagging trials (Government Bay)
- 2018 preliminary project (28 receivers, 25 V9 tags)
- 2019-2021 full project (200 tags, 120 receivers)
- 2020 winter- capture fish under ice (gill nets)
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# Capture
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- Electrofishing (night)
  - Peak spawn- approximately November 15
  - <4 m water depth during spawn
  - not available before/after spawning (fish are deep!)
  - ~ 84% survival (6 months)
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# Capture
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- Gill net 
  - Very effective during fall- USFWS
  - Difficult or no recovery, rope burns, lost scales
  - Tried under ice gill nets, ~20 min soak, ~ 8% survival (6 months)
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<img src="data:image/png;base64,#../images/inside_ice_shanty_cisco_tagging_winter.JPG" width="18%" height="18%"/>
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# Post-capture care
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- Minimize handling time
- Capture <10 fish, transfer fish to waiting "transport boat", tagged
on shore
- Hold fish in flow-through .red[ROUND] tank (> 1 m) with .red[FLOW]
- Surgery immediately after fish "recover" from electrofishing
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# Surgery
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- Tent, heater to prevent ice formation on fish and us!
- V9 tags, fish ~ 400 mm TL, water temp 4-5 C
- Record TL, no external tag
- TENS electro-immobilisation
- <2 min surgery, 2 sutures
- Constant water flow over gills
- < 1 hour from capture to releases
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# Recovery

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- Fish released when able to maintain orientation
- Dedicated nurse- gently "assist" fish when upside down
  - Upside down cisco needs care to prevent death!
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# Tanks and flow

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- Round tanks critical, flow through
  - Rectangular/oval/cattle troughs result in "stuck fish"
- How much flow?
  - Fish should be swimming against current away from side ("endless
    pool")
  - Insufficient flow- fish turn upside down
  - Excessive flow- fish scrape tank sides
  - We used submersable utility pumps, short hoses, clamps to regulate
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# Take-home ideas

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- Minimize handling, time in tanks
- Round tanks are critical
- Sufficient water flow in tanks to promote swimming, flow-through 
- TENS electro-immobilisation- quick recovery
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